Medullary thyroid carcinoma (MTC) is a rare cancer resulting from canceration of C cells of the thyroid gland. MTC is treated by surgical excision, but this has a problem that it caused reduced Quality of Life (QOL) for patients.
The irinotecan (CPT-11) which is a camptothecin derivative has the potential for efficacy against MTC, but CPT-11 has a short half-life and produces serious side-effects, and therefore its use has been limited (NPL 1).
When an anticancer agent is encapsulated in liposomes, it is known that accumulation of the drug in the tumor increases by passive targeting, allowing side-effects to be reduced. Further, modification of the liposomes with a ligand can also enhance the therapeutic effect of the liposomes. For example, treatment of breast cancer and stomach cancer has been attempted using anticancer agents such as cantharidin or dihydrotanshinone encapsulated in liposomes modified with octreotide (Oct) which is a high-affinity ligand for somatostatin receptor (SSTR) (NPL 2 and 3).
The present inventors have previously prepared Oct-modified CPT-11-encapsulating liposomes, and have reported that they exhibit in vitro cytotoxicity against MTC-derived cell lines that express SSTR (NPL 4). However, no effective in vivo method has been established for treatment of MTC.